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The harmful effects of shoeing |
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Page 2 of 3
Dr. C.C. Pollit, at the University of Queensland, Australia, showed in his 1993 study of circulation in the hoof that a shod hoof is not supplied with blood in the normal fashion, but through an alternate route.
Professor Smedegards' publications make clear that shoeing prevents the hoof mechanism from working, if for no other reason that the horse is forced to walk unnaturally (the whole hoof impacts the ground at the same time, and the horse cannot break over naturally). A normal hoof contacts the ground first at the rear and side, then breaks over.
So from various sources throughout history, we can see it is known that:
1. shoeing causes the foot to become contracted (Clark)
2. shoeing causes a deviance of the normal laminae structure (Zierold)
3. the impact forces with each shod step are much greater, and the vibration of the shoe is damaging (Bein)
4. circulation is decreased through shoeing (Pollitt)
5. the side walls, at the widest part of the hoof, have to be able to move outward (Smedegard) All these are veterinary professionals, though there are many other scientists who have added interesting dissertations to this topic.
Personal Observations:
"Hoof mechanism" is the term given to the movement of the hoof capsule. It has long been known and measured that, when weightbearing, the downward force of the skeleton on the front wall of the hoof capsule forces the coronet band, at its highest point, to sink downward and inward. This illustration is well known and accepted.
However, the downward-inward movement of the coronet band is possible only if the neighboring side walls can move outwards, or can sink into soft ground. This movement is coupled with the flattening of the concave sole, which makes room for the descending coffin bone. This way, the solar corium is not bruised but rather is relaxed, and the capillaries in the sole and wall fill with blood. It is also known, and clearly illustratable (through infrared photography) that shod feet are cool, whereas unshod feet are warm.
This means that, at the widest part of the hoof (not only in the area of the heel), a considerable expansion of the hoof capsule takes place upon weightbearing. The wall expands NOT ONLY in the rearmost third of the hoof, as shown in many textbooks. Elementary pythagorean geometry supports this. For a normal warmblood, the concave sole must sink down about 1cm, which necessitates an expansion of the wall of about 1mm to each side. At higher speeds, the bulb of the heel contacts the ground first, which adds to the widening of the foot. Repeatedly, expansion of up to 4mm to each side have been found through live "prints" at the trot and canter.
A shod hoof is unable to expand as necessary, the concave sole cannot draw flat, and the solar corium is bruised as a result. When trimming such hooves, these bruises become visible. To get back to L. Bein's findings on shock absorption. The expansion of the hoof capsule complete with the flattening of the sole absorb up to 80% of the impact force. In terms of physics, this is conversion of of energy through reversible deformation.
The consequences of the lack of up to 80% of shock absorption are widely known as arthritis, tendonitis, etc. The damage done is all the greater when the horse is young, and the still-developing coffin bone is handicapped in its development to proper size through shoeing. Shoeing a horse under 3 (or even 2) years results in crippled and deformed coffin bones and steep, contracted hooves. The negative effect of shoes on joints and tendons is increased through stresses during motion, ie. the weight of the shoe stressing the joint and tendon through centripedal force. The heavier the shoe, the greater this force.
The contracting effect of shoes increases from day to day, since the hoof grows continually, not straight down but in a conical shape. The hoof grows in width, but the shoe does not; after a month, the hoof grew by 1 cm, in length and width; with a shoe, only in length, forcing a constriction of the corium. That a horse with such damage is still able to walk is due largely to the fact that the nerves have mostly become nonfunctional. As soon as the shoes are removed, circulation begins to return, and after a while the nerves "come back to life." So the damage will be present for years before the horse goes lame (due to inflammation, which brings circulation, and as such nerve activity).
The lack of circulation grows more severe with lack of movement. A shod horse which is worked all day tilling the field, for example, has better circulation than a shod horse standing in a box stall and ridden an hour a week.
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